December 25, 2013

Life will end in half a billion years: don't worry, it won't be your fault

Life and Earth as we know them, will end, but it won't be human induced - not even by global warming. Those last two points will disappoint a few billion people, who daily long for Armageddon, purely for the joy of being able to say 'I told you so'.

Earth, for example, is 4.6 billion years old, but animal life has been
around for only half a billion years, and oxygen has only been abundant
in the atmosphere for two billion years or so and, of course,
intelligent life only a sliver of that time. If we found an analogue of
Earth circa three billion years ago, would we even recognize it as a
promising place?

The book’s title, Billings says, is a reference to the expected
longevity of life on Earth, but his account is less about exoplanets
than about the people who make the search for them their lives’ cause —
“creatures that, before their sun went dim, might somehow touch the
stars.”

There is both good and bad news here. The good news, Billings reports,
is that even if we burn up all the fossil fuel, we are unlikely to tip
Earth into “a runaway-­greenhouse world” as one scientist described
Venus.

The bad news is the planet is going to become uninhabitable anyway. Long
before the Sun burns out, Earth’s core will cool off and volcanoes,
which restore the atmosphere, will cease. The amount of carbon dioxide
will fall to levels too low to support photosynthesis in half a billion
years or so.

Complex life arose here only half a billion years ago, notes James
Kasting, a geosciences professor at Penn State, who concludes glumly
that intelligence might exist for only one-tenth of Earth’s history,
cutting the odds of its being detected elsewhere.

Did you notice that little bit in there? Carbon dioxide, currently labelled, for marketing reasons, a pollutant, and source of all evil, despite remaining one of a handful of elements essential for any and all life, will fall to levels that are too low - in half a billion years.